The present invention relates in general to a skive mechanism for stripping receiver members from fuser apparatus rollers of reproduction apparatus, and more particularly to a skive mechanism including a contact skive assembly and an air skive for fuser apparatus rollers which will substantially prevent damage to the rollers and to the fused image on the receiver members stripped from the rollers.
In typical commercial reproduction apparatus (electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member. An electric field, such as provided by a corona charger or an electrically biased roller, is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is separated from the dielectric member and transported away from the dielectric member to a fuser apparatus at a downstream location. There the image is fixed to the receiver member by heat and/or pressure from the fuser apparatus to form a permanent reproduction on the receiver member.
One type of fuser apparatus, utilized in typical reproduction apparatus, includes at least one heated roller and at least one pressure roller in nip relation with the heated roller. The fuser apparatus rollers are rotated to transport a receiver member, bearing a marking particle image, through the nip between the rollers. The pigmented marking particles of the transferred image on the surface of the receiver member soften and become tacky in the heat. Under the pressure, the softened tacky marking particles attach to each other and are partially imbibed into the interstices of the fibers at the surface of the receiver member.
Accordingly, upon cooling, the marking particle image is permanently fixed to the receiver member. It sometimes happens that the marking particles stick to the peripheral surface of the heated roller and result in the receiver member adhering to such roller; or the marking particles may stick to the heated roller and subsequently transfer to the peripheral surface of the pressure roller resulting in a receiver member adhering to the pressure roller.
In view of the receiver member adherence problem, a skive mechanism, including mechanical skive fingers or separator pawls for example, has been employed to engage the respective peripheral surfaces of the fuser apparatus rollers to strip any adhering receiver member from the rollers in order to substantially prevent receiver member jams in the fuser apparatus. Typically a fuser apparatus skive mechanism includes a plurality of skive fingers. The skive fingers are generally formed as elongated members respectively having a relatively sharp leading edge urged into engagement with a fuser apparatus roller. For example, the skive fingers may be thin, relatively flexible, metal shim stock. The respective leading edge of each of the skive fingers is directed in the opposite direction to rotation of the fuser apparatus roller with which such skive finger is associated so as to act like a chisel to strip any receiver member adhering to such roller from the peripheral surface thereof.
However, if the marking particle image is particularly dense, the receiver member may adhere to a fuser apparatus roller with such force that engagement with the skive fingers does not completely strip the receiver member from the roller. When a receiver member transported through the fuser apparatus is only stripped from a roller by some of the skive fingers (and not by others), the receiver member will cause a jam in the fuser apparatus. This destroys the reproduction formed on the receiver member and shuts down the reproduction apparatus until the receiver member is cleared from the fuser apparatus. Moreover, as the receiver member moves with the fuser apparatus roller to which it adheres, the stripped portions of the receiver member are forced into engagement with their associated skive fingers by the non-stripped portions of the receiver member. The engagement force of the receiver member on the skive fingers may be sufficient to flex those skive fingers so as to engage the associated peripheral surface of the fuser apparatus roller at a substantially increased attack angle. This increased attack angle may then damage the roller by gouging its peripheral surface or may damage the skive finger itself. Alternatively, as the receiver member is transported through the fuser apparatus, the receiver member may apply such force to the skive fingers on initial engagement therewith so as to cause such fingers to buckle in the direction which will flex those skive fingers to engage the associated fuser apparatus roller at an increased attack angle. Again, this increased attack angle may damage the roller by gouging its peripheral surface or may damage the skive finger itself.
It has been shown in U.S. Pat. No. 5,532,810 (issued Jul. 2, 1996, in the name of Cahill); U.S. Pat. No. 5,589,925 (issued Dec. 31, 1996, in the name of Cahill); and U.S. Pat. No. 6,029,039 (issued Feb. 22, 2000, in the name of Aslam et al.) that providing elongated skive fingers of limited flexibility mounted respectively in particularly configured support bodies substantially prevents damaging flex of the skive fingers. In these prior skive mechanisms, the support bodies support a major portion of the skive fingers and pivot into engagement with the fuser roller to limit skive finger flexing when engaged by a receiver member to be stripped from a fuser roller. The skive fingers are also shown as being retractable to prevent damage induced by jammed receiver members.
Another skive mechanism, which can overcome problems generated by mechanical skive fingers, includes air jets directed at the rollers to strip any adhering receiver member from the rollers (see for example U.S. Pat. No. 4,420,152 (issued Dec. 13, 1983, in the name of Miyashita). It provides an air chamber with exhaust nozzles which direct escaping air at high speeds for separating receiver members from the fuser rollers. However such arrangement creates a high pressure area near the fusing nip and a low pressure area adjacent to the air skive. Thus after a receiver member is stripped from a fuser roller it is attracted to the skive structure. Since the skive structure is close to the fuser roller, it is at an elevated temperature. Accordingly, the hot skive structure may scratch the image on the receiver member or damage the receiver member itself.
In view of the above, this invention is directed to a fuser apparatus having a pair of rollers in nip relation to transport a receiver member therebetween to permanently fix a marking particle image to such receiver member, and a skive mechanism for stripping a receiver member adhering to a fuser apparatus roller from the said roller. The skive mechanism includes a frame located in spaced relation with one of the rollers of the pair of fuser apparatus rollers. A plurality of skive assemblies, mounted on the frame, each include a skive finger and a support body for supporting such skive finger in operative relation to such one of the rollers. The skive fingers are elongated, thin, flexible members to substantially prevent damage to such associated fuser apparatus roller. Further, an air plenum is provided in operative relation to the other of the pair of rollers of the fuser apparatus rollers. The air plenum has a nozzle arrangement directed at an angle to the fuser apparatus roller associated with the air plenum so as to provide a positive air flow to substantially assure that a receiver member adhering to such fuser apparatus roller is stripped therefrom.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.